1. Field of the Invention
The present invention relates to a composite circuit board having a thick circuit conductor and thin circuit conductor, and its manufacturing method.
2. Description of the Related Art
A circuit board through which a relatively large electrical current, for example, one for driving a motor flows requires a circuit conductor having a large cross-sectional area. A conventional circuit board of this type has a structure in which a punched-out circuit conductor made by punching out a desirable circuit pattern from a metal plate (copper, aluminum, etc) is integrally fixed on an insulation substrate (see Published Unexamined Japanese Patent Application (PUJPA) No. 63-237495).
In such a circuit board, to fix a punched-out circuit conductor on an insulation substrate, a copper foil pattern is formed on an insulation substrate, and a punched-out circuit conductor is soldered thereon. This is rather a complicated procedure. Further, the punched-out circuit conductor, which is relatively thick, inevitably creates a bump on the surface of the insulation substrate for its thickness, causing great irregularity on the circuit substrate surface and making matters difficult for printing of a solder resist and circuit conductor to be multi-layered.